Apparatus of high power density fuel cell layer with micro structured components

ABSTRACT

A fuel cell layer with a fuel plenum, an oxidant, and a plurality of fuel cells, wherein each fuel cell has a porous substrate, a channel, an anode and a cathode formed in opposite channel walls, an electrolyte contacting the anode and the cathode preventing transfer of fuel to the cathode and transfer of oxidant to the anode, a coatings to prevent fuel or oxidant from entering a portion of the porous substrate, a first sealant barrier disposed on the first side and the second sealant barrier disposed on the second side, and a positive and a negative electrical connection disposed on the second side, wherein multiple fuel cells are connected and the fuel cell assembly generates a current to drive an external load.

CROSS-REFERENCES TO RELATED APPLICATION(S)

The application herein claims priority from the provisional PatentApplication 60/354,795 with a filing date of Feb. 6, 2002.

FIELD OF THE INVENTION

The present invention relates to fuel cells. More specifically theinvention relates to a fuel cell layer comprising multiple cells formedwithin a channel formed using porous substrates.

BACKGROUND OF THE INVENTION

High power density fuel cells have long been desired.

Existing fuel cells generally are a stacked assembly of individual fuelcells, with each cell producing high current at low voltage. The typicalcell construction involves reactant distribution and current collectiondevices brought into contact with a layered electrochemical assemblyconsisting of a gas diffusion layer, a first catalyst layer, anelectrolyte layer, a second catalyst layer and a second gas diffusionlayer. With the exception of high temperature fuel cells, such as moltencarbonate cells, most proton exchange membrane, direct methanol, solidoxide or alkaline fuel cells have a layered planar structure where thelayers are first formed as distinct components and then assembled into afunctional fuel cell stack by placing the layers in contact with eachother.

One major problem with the layered planar structure fuel cell has beenthat the layers must be held in intimate electrical contact with eachother, which if intimate contact does not occur the internal resistanceof the stack increases, which decreases the overall efficiency of thefuel cell.

A second problem with the layered planar structured fuel cell has beento maintain consistent contact between the layers for sealing andensuring correct flows of reactants and coolants in the inner recessesof the layer structured fuel cell. Also if the overall area of the cellbecomes too large then there are difficulties creating the contactingforces needed to maintain the correct fluid flow distribution ofreactant gases over the electrolyte surface.

Existing devices also have the feature that, with the layered planarstructure fuel cell since both fuel and oxidant are required to flowwithin the plane of the layered planar structured fuel cell, at least 4and up to 10 but typically 8 distinct layers have been required to forma workable cell, typically a first flowfield, a first gas diffusionlayer, a first catalyst layer, a first electrolyte layer, a secondcatalyst layer, a second gas diffusion layer, a second flowfield layerand a separator. These layers are usually manufactured into separatefuel cell components and then the layers are brought into contact witheach other to form a fuel cell stack. When contacting the layers caremust be taken to allow gas diffusion within the layers while preventinggas leaking from the assembled fuel cell stack. Furthermore, allelectrical current produced by the fuel cells in the stack must passthrough each layer in the stack, relying on the simple contacting ofdistinct layers to provide an electrically conductive path. As a result,both sealing and conductivity require the assembled stack to be clampedtogether with significant force in order to activate perimeter seals andreduce internal contact resistance.

The manufacture of the layers for existing fuel cell configurations isoften expensive and difficult. The bipolar plates, which serve asoxidant and fuel flowfields as well as the separator are oftenconstructed from graphite which is difficult to machine, addingsignificant cost to the fuel cell stack. The membrane electrode assembly(MEA) is usually constructed by first coating a solid polymerelectrolyte with catalyst on either side and then pressing gas diffusionelectrodes onto the electrolyte. The fuel cell assembly requiresmultiple individual bipolar plates and membrane electrode assemblies tobe connected together in a serial manner. Usually discrete seals must beattached between neighbouring bipolar plates and membrane electrodeassemblies and the whole stack of sealed bipolar and MEA layers must beheld together under considerable compressive force.

A need has existed to develop alternative fuel cell designs that do notperpetuate the approach of assembling discrete layers in a serialmanner. One way to meet this need is to build fuel cells using amicro-structured approach wherein microfabrication techniques andnano-structured materials can be combined to create novel devices notsubject to the problems commonly associated with conventional fuel celldesigns. The application of microscale techniques to fuel cells has anumber of distinct advantages. Specifically, the potential for increasedpower density due to thinner layers and novel geometries, improved heatand mass transfer, improved and/or more precise catalyst utilization andreduced losses with shorter conductive path lengths will all make fuelcells more efficient and enable higher volumetric power densities. Theopportunity to include ancillary systems into the fuel cell design andthe potential for new applications to emerge present even more potentialbenefits.

A need has existed for a micro fuel cell capable of low costmanufacturing because of having fewer parts than the layered planarstructure fuel cell.

A need has existed for a micro fuel cell having the ability to utilize awide variety of electrolytes.

A need has existed for a micro fuel cell, which has substantiallyreduced contact resistance within the fuel cell.

A number of prior inventions have used microscale-manufacturingtechniques with fuel cells. U.S. Pat. No. 5,861,221 presents a ‘membranestrip’ containing a number of conventional MEAs connected to each otherin series by connecting the edge of the negative electrode of one MEA tothe edge of the positive electrode of the next MEA. Two configurationsare considered. The first constructs the ‘membrane strip’ by placing theMEAs together in a step-like configuration. The second constructs the‘membrane strip’ by combining MEAs end-to-end with electricallyconductive regions between them that connect the cells in series. Insome follow-up work (U.S. Pat. No. 5,925,477) the same inventorsincorporate a shunt between the electrodes to improve the electricalconductivity of the cell. The MEA's themselves are of conventionallayered structure design, and the overall edge collected assemblycontinues to rely on conventional seals between neighbouring MEA's.

U.S. Pat. No. 5,631,099 and U.S. Pat. No. 5,759,721 use similar seriesconnection concepts but apply a number of other microscale techniques tothe fuel cell design. By doing so multiple fuel cells are formed withina single structure simultaneously. The fuel cells themselves stillreside as layered planar devices mounted onto a carrier, withinterconnection between neighbouring fuel cells requiring a penetrationof the carrier layer. Most of the techniques discussed in these patentsrelate to the creation of methanol tolerant catalysts and theapplication of palladium layers to the catalyst to prevent methanolcrossover within the cells.

WO 01/95406 describes a single membrane device that is segmented tocreate multiple MEA structures. Complex bipolar plates that aredifficult to manufacture provide both fuel and oxidants to both sides ofthe MEA layer. U.S. Pat. No. 6,127,058 describes a similar structure,but instead of complex manifolding of reactant gases, only one reactantis supplied to either side of the MEA layer. Series interconnection ofthe fuel cells formed within the single MEA layer is achieved throughexternal current collectors arranged around the perimeter of the deviceproviding electrical connection from the top of the MEA layer to thebottom of the MEA layer. Such perimeter electrical connections areinefficient.

Some prior art fuel cells attempt to reduce size and fabrication costsby applying microfabrication techniques. For example the Case WesternReserve University device forms multiple fuel cells on a carriersubstrate using thin layer processes similar to those used in printingand semiconductor fabrication (Wainwright et al. “A microfabricatedHydrogen/Air Fuel Cell” 195 Meeting of the Electrochemical Society,Seattle, Wash., 1999). In these designs the fuel cells remain ofconventional planar design, with the exception that the fuel cells arebuilt-up on a base substrate. The cathodes must be formed on top of theplanar electrolytes and then must be connected to neighbouring anodeswith an explicit interconnect.

All the cells presented above use current collection on the edge of theelectrode. This significantly increases the internal cell resistance ofthese cells. Each of these cells is also based on solid polymerelectrolytes as this is the only electrolyte that allows for easymanufacture. Furthermore, all of the cells presented above achieve amicro fuel cell design by forming multiple fuel cells within a singleelectrolyte plane.

The concept of using non-planar electrolytes has been considered in thepast. GB 2,339,058 presents a fuel cell with an undulating electrolytelayer. In this configuration a conventional layered MEA is constructedin an undulating fashion. This MEA is placed between bipolar plates.This design increases the active area that can be packed into a givenvolume. However, this design still relies on the expensive andcomplicated layered structure with explicit seals and requirescompressive force to maintain internal electrical contact and sealing.JP 50903/1996 presents a solid polymer fuel cell having generally planarseparators with alternating protruding parts serving to clamp a powergeneration element (apparently an MEA) into a non-planar but piecewiselinear shape. As with GB 2,339,058, this document continues to rely onthe expensive and complicated layered structure but this design alsoputs undue stress on the MEA by forcing it into a non-planar arrangementusing the separator plates.

In addition to non-planar designs, some prior art presents tubularconfigurations. U.S. Pat. No. 6,060,188 presents a cylindrical fuel cellwith a single MEA layer formed into a cylinder. Fuel or oxidant isdelivered to the interior recess of the cylinder with the other reactantdelivered on the exterior. Within this design, each cylindricalstructure creates a single cell, with current flowing through theannular cylindrical wall that is the fuel cell. A method of providingseries electrical interconnection between fuel cells or of sealingindividual fuel cells is not disclosed. This design is reminiscent oftubular designs for solid oxide fuel cells that are well known.

A need has existed to develop fuel cell topologies or fuel cellarchitectures that allow increased active areas to be included in thesame volume, i.e. higher density of active areas. This will allow fuelcells to be optimized in a manner different than being pursued by mostfuel cell developers today.

SUMMARY OF THE INVENTION

The present invention relates to a specific fuel cell layer architecturethat is of an integrated design in which the functions of gas diffusionlayers, catalyst layers, and electrolyte layers are integrated into asingle substrate. This integrated design enables simpler manufacturingprocesses and scaling of the design.

The invention is also a fuel cell layer with a fuel plenum, an oxidant,and a plurality of fuel cells. The fuel cell has a porous substrate, achannel, an anode and a cathode formed in opposite channel walls, anelectrolyte contacting the anode and the cathode preventing transfer offuel to the cathode and transfer of oxidant to the anode, a coatings toprevent fuel or oxidant from entering a portion of the porous substrate,a first sealant barrier disposed on the first side and the secondsealant barrier disposed on the second side, and a positive and anegative electrical connection disposed on said second side. Multiplefuel cells are connected and the fuel cell assembly generates a currentto drive an external load.

The fuel cell layer is created by forming an assembly of single channelfuel cells to create a layer with an anode side and a cathode sideenclosing a plurality of fuel cells that are series connected within thelayer. When microscopic dimensioned channels are used the result is avery high power density arrangement of fuel cells in a confined volume.

A number of variations on the design of the fuel cell layer areenvisioned. Some of the variations include having the fuel and oxidantplenums dead-ended, having the fuel cell layer enclosing a volume,having the porous substrate in a non-planar, or alternately planar,configuration and having the fuel cell layer enclose a volume in acylindrical shape. The substrate can be formed from a variety ofconductive and non-conductive porous media.

Dimensionally, the channels can have a dimension ranging from 1nanometer to 10 cm in height, 1 nanometer to 1 mm in width and from 1nanometer to 100 meters in length. A single fuel cell of the inventionis contemplated of being capable of producing between approximately 0.25volts and approximately 4 volts.

Between 1 and 5000 fuel cells are contemplated as usable in one fuelcell layer in this design, however in a preferred embodiment, the fuelcell layer has between 75 and 150 joined fuel cells. This fuel celllayer is contemplated to be capable of producing a voltage between 0.25volts and 2500 volts. A fuel cell with more channels will be capable ofproducing higher voltages.

Electrolyte usable in this invention can be a gel, a liquid or a solidmaterial. It is contemplated that the electrolyte can be between 1nanometer and 1.0 mm in thickness, or alternatively simply filling eachchannel from first wall to second wall without a gap. Having a thinchannel, and therefore a thin electrolyte, increases the efficiency ofthe fuel cell.

The fuel cell layer of the invention can be used by first, connecting afuel source to a fuel plenum inlet; second, connecting a fuel plenumoutlet to a re-circulating controller; third, connecting an oxidantplenum inlet to an oxidant source; fourth, connecting an oxidant plenumoutlet to a flow control system, fifth, connecting a positive electricalconnection and a negative electrical connection to an external load;sixth, flowing fuel and oxidant to the inlets; and finally, driving loadwith electricity produced by the fuel cell.

BRIEF DESCRIPTION OF THE FIGURES

A specific embodiment of the invention will be described by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a first embodiment of the inventivefuel cell;

FIG. 1 a is a cross-sectional detailed view of the anode with thecatalyst at a first depth in the porous substrate;

FIG. 1 b is a cross sectional detailed view of the anode with thecatalyst at a second depth in the porous substrate;

FIG. 1 c is a cross sectional detailed view of the cathode;

FIG. 2 is a cross-sectional view of a dead ended embodiment of theinventive fuel cell;

FIG. 2 a is embodiment of the fuel cell according to the invention withthe fuel and oxidant plenums being solid with flow channels containedtherein;

FIG. 3 is a cross-sectional view of another embodiment of a dead endedfuel cell;

FIG. 3 a is an embodiment of the invention with an oxidant plenum opento the ambient environment;

FIG. 3 b is an embodiment of the invention with a fuel plenum open tothe ambient environment;

FIG. 4 is a cross-sectional view of a fuel cell layer formed bycombining multiple fuel cells of the type described in FIG. 1;

FIG. 4 a is a cross sectional view of a multiple porous substrate fuelcell layer with the fuel plenum open to the ambient environment;

FIG. 4 b is a cross sectional view of a multiple porous substrate fuelcell layer with the oxidant plenum open to the ambient environment;

FIG. 4 c is a cross sectional view of a fuel cell layer with up to 5000fuel cells;

FIG. 5 is a cross-sectional view of a fuel cell with multiple fuel cellsof the type described in FIG. 1 formed within a single substrate;

FIG. 5 a is another embodiment of a fuel cell with multiple cells;

FIG. 6 is a perspective view of a fuel cell layer containing multiplefuel cells of the type described in FIG. 1;

FIG. 7 is another detailed perspective view of the fuel cell of theinvention with undulating channels;

FIG. 8 is a perspective view of a cylindrical version of a fuel cellaccording to the invention;

FIG. 8 a is a cross-sectional view of an embodiment of the fuel cell ofFIG. 1 in which the substrate is irregularly shaped;

FIG. 9 is a cross sectional view of a cylindrical version of a fuel cellaccording to the invention;

FIG. 10 is another embodiment of the inventive fuel cell of theinvention with the channels in the form of a set of stacked annularrings;

FIG. 11 is another embodiment of the inventive fuel cell with thechannels in the form of a spiral around the cylinder; and

FIG. 12 is a perspective view of a bi-level fuel cell structure.

DETAILED DESCRIPTION OF INVENTION

The present invention relates to a microstructure fuel cell having asubstrate, which is preferably porous, an assembly of fuel cells havinga single or multiple substrate structure and methods for manufacturingsuch fuel cells and fuel cell layers.

The invention relates to a specific fuel cell architecture that is of anintegrated design in which the functions of gas diffusion layers,catalyst layers, and electrolyte layers are integrated into a singlesubstrate. This architecture makes it possible to fold together thevarious ‘layers’ of which a working fuel cell is formed and producelinear, curvilinear, undulating or even fractal shaped electrolyte pathsthat allow for higher volumetric power density to be achieved byincreasing the electrochemically active surface area. In addition, byforming the various fuel cell layers within a single substrate theproblem of simple contacting of fuel cell components to createelectrical connections is eliminated, thus creating the potential forlower internal cell resistances to be achieved. The cell layersthemselves can be constructed in planar, non-planar or involuteconfigurations providing further advantages in increasing surfaces areasand providing flexibility in applications. This integrated designenables simpler manufacturing processes and scaling of the design.

Unlike existing fuel cell designs, the present invention, in oneembodiment, provides convoluted electrolyte layers, which do notsmoothly undulate. Other embodiments of the invention include shapesthat are essentially non-smooth. Utilizing such non-smooth electrolytepaths allows for greater overall surface areas for the fuel cellreactions to be packed into a given volume than can be achieved whenplanar electrolyte layers are employed as in conventional fuel celldesigns. The present invention also allows for significantly decreaseddistances between separate electrolyte layers, thereby allow for agreater surface area in a given volume than conventional designs.

The present invention contemplates the use of a design inspired byfractal patterns, which provides long electrolyte path lengths. Theinvention includes a method for building fuel cells and “stacks” thatare not dependent on the layered process and which do not require thepost-manufacturing assembly of distinct layered components. Theconventional relationship between MEA layers and bipolar plates iseliminated, as is the reliance on multiple discrete layered structures.The invention also contemplates a design with individual fuel cellsturned on their side relative to the overall footprint of the assembledfuel cell device. The invention contemplates building multiple fuelcells with an integrated structure on a single substrate using parallelmanufacturing methods.

Specifically, it is contemplated to use a porous substrate for the fuelcell through which reactant gas will diffuse with little driving force.The substrate may or may not be electrically conductive. If it isconductive, it is contemplated to insulate at least a portion of thesubstrate, which typically would separate the anode from the cathode,this insulation may be formed by the electrolyte separating the anodefrom the cathode and, if necessary, an optional insulating structuralmember may be added. More specifically, the fuel cell is contemplated tohave: (a) a fuel plenum comprising fuel; (b) an oxidant plenumcomprising oxidant; (c) a porous substrate communicating with said fuelplenum, and said oxidant plenum further comprising a top, a bottom, afirst side, and a second side; (d) a channel formed using said poroussubstrate, wherein said channel comprises a first channel wall and asecond channel wall; (e) an anode formed from a first catalyst layerdisposed on the porous substrate of said first channel wall; (f) acathode formed from a second catalyst layer disposed on the poroussubstrate of said second channel wall; (g) electrolyte disposed in atleast a portion of said channel contacting the anode and the cathodepreventing transfer of fuel to the cathode and preventing transfer ofoxidant to the anode; (h) a first coating disposed on at least a portionof said porous substrate to prevent fuel from entering at least aportion of said porous substrate; (i) a second coating disposed on atleast a portion of said porous substrate to prevent oxidant fromentering at least a portion of said porous substrate; (j) a firstsealant barrier disposed on the first side and the second sealantbarrier disposed on the second side; (k) a positive electricalconnection disposed on said first side; (l) a negative electricalconnection disposed on said second side; and wherein the resulting fuelcell generates current to drive an external load.

Referring to FIG. 1, which is a cross-sectional view of one embodimentof the invention, a fuel cell 8 has an optional fuel plenum 10containing fuel 11. A porous substrate 12 is adjacent the optional fuelplenum 10. The fuel plenum can have an optional fuel plenum inlet 18.The fuel plenum can also have an optional fuel plenum outlet 20. Anoptional oxidant plenum 16 containing oxidant 13 is adjacent the poroussubstrate 12. The oxidant plenum can have an optional oxidant plenuminlet 52. The oxidant plenum can also have an optional oxidant plenumoutlet 54. If no oxidant plenum is used the fuel cell uses the ambientenvironment as a source of oxidant.

The porous substrate 12 can have a shape that is rectangular, square ororthogonal or alternatively, it can be irregularly shaped. In thisembodiment it is pictured as being formed within a single plane,although non-planar substrates or multiple substrate configurations areenvisioned.

A channel 14, formed using the porous substrate, can be straight or ofarbitrary design. If of arbitrary design the channel is referred tothroughout this application as “undulating.” If multiple channels arepresent at least one may be undulating. The channel 14 has a firstchannel wall 22 and a second channel wall 24. Additionally the poroussubstrate 12 has a top 100, bottom 102, first side 104 and a second side106.

Said channel can comprise an undulating channel, a straight channel oran irregular channel. If undulating, the channel can be sinusoidal inshape and if undulating, the channel may be of a shape that is in atleast three planes.

An anode 28 is created on or alternately in the surface of the firstchannel wall 22, although the anode could be embedded in the wall aswell. Anode 28 is created using a first catalyst layer 38 on or into thesurface of the first channel wall 22.

A cathode 30 is formed on the surface or alternately in the secondchannel wall 24. Like the anode 28, the cathode 30 could be embedded inthe second channel wall 24. Cathode 30 is created using a secondcatalyst layer 40.

FIGS. 1 a, 1 b and 1 c provide details of the cathode and anode of thefuel cell. FIG. 1 a shows the anode 28 at a first depth within theporous substrate 12, FIG. 1 b shows the anode 28 at a second depthwithin the porous substrate 12 and FIG. 1 c shows the cathode 30.

The catalyst layers can be deposited on the first and channel walls orcan be formed in the channel walls. In one embodiment the first andsecond catalyst layers are disposed in the porous substrate to at leasta minimum depth to cause catalytic activity.

Referring back to FIG. 1, an electrolyte 32 is disposed in the channel14.

A first coating 34 is disposed on at least a portion of the poroussubstrate 12 preventing fuel from entering at least a portion of theporous substrate 12. A second coating 36 is disposed on at least aportion of the porous substrate 12 preventing oxidant from entering atleast a portion of the porous substrate 12.

A first sealant barrier 44 is disposed on the first side of the poroussubstrate and a second sealant barrier 46 is disposed on the second sideof the porous substrate. The sealant barriers can optionally be disposedwithin a sealant barrier channel 43.

A positive electrical connection 50 is engaged with the porous substrate12 on the first side of the porous substrate.

A negative electrical connection 48 is engaged with the porous substrate12 on the second side of the porous substrate.

The resulting fuel cell generates current 56 to drive an external load58.

FIG. 2 is another embodiment of the invention showing a dead endedversion of the fuel cell 108 specifically excluding the fuel outlet 20and the oxidant outlet 54 of the FIG. 1 embodiment.

In the embodiments of the invention depicted in FIGS. 2 and 2 a, it iscontemplated that the electrolyte 32 can be mounted in the channel 14 atan angle 76, preferable at an angle, which is perpendicular to thelongitudinal or horizontal axis 74 of the predominant portion of theporous substrate 12.

In FIG. 2 an optional support member 26 separates first channel wall 22from second channel wall 24 however the support member is not requiredin every embodiment. Some alternatives envision multiple support membersas shown in FIG. 2 a. Between one and 50, or more support members arecontemplated herein.

Now referring to FIG. 2 a, a fuel cell is shown with a solid fuel plenum10 with flow fields 126 and a solid oxidant plenum 16 with flow fields126. It is also envisioned that the fuel plenum comprises a permeablematerial containing the fuel. The oxidant plenum can also comprise apermeable material. It is understood that the fuel plenum and oxidantplenum need not be constructed in the same manner and a variety ofcombinations of oxidant and fuel plenum configurations can be used. Thefuel plenum and the oxidant plenum can each have a variety of shapes,round, elliptoid, rectangular or square. It is particularly contemplatedthat the fuel plenum has a rectangular cross-section.

FIG. 3 is a cross-section of another embodiment of a dead ended versionof the fuel 110 that excludes both the fuel inlet 18 and the fuel outlet20 as well as the oxidant inlet 52 and the oxidant outlet 54 of theembodiment of FIG. 1. FIG. 3 a shows an embodiment of the fuel cellwhere the oxidant plenum 16 is entirely removed. In such an embodimentthe cell would use the ambient environment as an oxidant supply. FIG. 3b shows an embodiment of the fuel cell where the fuel plenum 10 isremoved entirely. In this configuration the fuel cell uses the ambientenvironment as a fuel supply.

FIG. 4 shows a first fuel cell 66 formed from a substrate 12 that ismade adjacent a second fuel cell 114 formed from a second substrate 62.The first and second fuel cells may be formed from either theassociation of multiple substrates or, as shown in FIG. 5, the firstfuel cell 66 and the second fuel cell 114 may be formed by creatingmultiple channels 14 within a single substrate 12.

In FIG. 4, a plurality of fuel cell structures are formed using separateporous substrates and they are then connected to each other at saidsealant barriers 44 forming a fuel cell layer. In this figure a firstfuel cell 66 is connected to a second fuel cell 114. Multiple fuel cellscan be connected together in this manner to create a fuel cell layer 64with a fuel side 116 and an oxidant side 118. The details in the figurecan be easily understood by referring to the items numbers in thedescription of FIG. 1 and will therefore not be elaborated here.

In this embodiment it is envisioned that the fuel cell be connected inseries, in parallel or in combinations thereof to allow the fuel celllayer to produce current to drive an external load.

FIG. 4 a shows a fuel cell layer with the fuel plenum open to theambient environment. FIG. 4 b shows a fuel cell layer with the oxidantplenum open to the ambient environment. In this figure at least oneoptional support member 26 is shown on at least one of said fuel cells.

FIG. 4 c shows an embodiment of said fuel cell layer wherein up to 5000cells are connected together in the manner explained for FIG. 4.

In FIG. 5, the same fuel cell structures are formed in a single poroussubstrate 12. In this embodiment a plurality of fuel cells are createdwithin the porous substrate in the same manner as described for FIG. 1.Since, in this case, the fuel cells are formed within a single substratethe sealant barriers and electrical connections associated with eachfuel cell are not required. Instead a first sealant barrier 44 isdisposed on the first side of the porous substrate, a second sealantbarrier 46 is disposed on the second side of the porous substrate and aplurality of third sealant barriers 45 are disposed between said fuelcells. The sealant barriers provide gas impermeable separators betweenthe fuel cells within the fuel cell layer.

It is understood that the same embodiments shown for the multiplesubstrate structure in FIGS. 4 a, 4 b and 4 c can be used with thesingle substrate structure shown in FIG. 5. Additionally the poroussubstrate 12 in FIG. 5, has first side 104 and a second side 106.

This association of two fuel cells, either by the structure of FIG. 4 orthe structure of FIG. 5, can be extended to place an arbitrary number offuel cells in association with each other. In both embodiments, the endsof the multiple structures are sealed with a sealant barrier 44 and asecond sealant barrier 46. In both embodiments, negative electricalconnection 48 is attached on one end of the multiple fuel cell assemblyand positive electrical connection 50 is attached on the other end ofthe multiple fuel cell assembly to allow the multiple fuel cell assemblyto drive an external electrical load.

The association of multiple fuel cells produces a fuel cell layer 64having a fuel side 116 that is brought into association with a fuelplenum 10 and an oxidant side 118 that is brought into association withan oxidant plenum 16.

If the substrate material from which the fuel cells within the fuel celllayer 64 is formed is conductive, then electrical current produced bythe individual fuel cells is able to flow directly through the substratematerial and the sealant barriers 44 to create a bipolar fuel cellstructure within the formed fuel cell layer. If the substrate materialfrom which the fuel cells within the fuel cell layer are formed is notelectrically conductive then the first coating 34 and second coating 36should both be made of an electrically conducting material and formed sothat the first coating 34 is in electrical contact with the anode 40while second coating 36 is in electrical contact with cathode 38. Thefirst coating 34 and the second coating 36 are also made in electricalcontact with the conductive sealant barrier 44. In either case, with aconductive or non-conductive substrate the electrical current producedby the fuel cell can be transported to the positive and negativeelectrical connections.

An alternate configuration for the fuel cell layer is shown in FIG. 5 a.In this configuration the first coating 34 is extended to connect theanode of the first fuel cell to the cathode of the second fuel cell. Thesecond coating 36 is likewise extended to contact the anode of the firstfuel cell. The first coating on the end and the second coating on theend can be used to connect the fuel cells on the ends to the positiveelectrical connection 50 and the negative electrical connection 48. Inthis configuration portions of the first coating are porous to allowfuel to reach the anode and portions of the second coating are porous toallow oxidant to reach the cathode. In this configuration neither theporous substrate nor the sealant barrier need be electricallyconductive. It is also envisioned that only the first coating beextended to provide electrical contact between the cells or that onlythe second coating be extended to provide electrical contact between thecells.

When multiple fuel cells are formed into a fuel cell layer, as describedin FIGS. 4 and 5 a series electrical connection of the individual fuelcells results. The summed voltages of the multiple fuel cells produce apotential difference between the positive and negative electricalconnections at either end of the fuel cell layer. A larger number offuel cells will enable the fuel cell layer to produce a higher voltagebetween the electrical connections. Any combination of conductive ornon-conductive substrates, barriers and caps may be used so long as anelectrically conductive path between neighbouring anodes and cathodes iscreated. In this manner either an edge collected or preferably a bipolarseries electrical connection of each of the fuel cells in the fuel celllayer is achieved without the need to clamp distinct components togetherand without the use of independently formed layered components. Also,the direction of current flow in the fuel cell layer is overall in theplane of the fuel cell layer rather than being orthogonal to the fuelcell layer as is the case in most current designs. It is also envisionedto electrically connect the fuel cells within a fuel cell layer togetherin parallel or in a combination of series and parallel.

FIG. 6 is a cutaway perspective view of a fuel cell layer 64. In thisfigure a first fuel cell 66 is separated from a second fuel cell 114 bya sealant barrier 44. A third fuel cell 115 is separated from the secondfuel cell 114 by another sealant barrier 44. The layer has the samestructure as the layers described in FIGS. 4 and 5. The single fuel celllayer 64 can contain as many sealant barriers and cells as desired. Thedetermination of the spacing between individual fuel cells within thefuel cell layer is at the discretion of the designer, limited bypragmatic issues of manufacturability and mass transport issues withinthe porous substrate.

The overall structure of the fuel cell layer 64 creates a seriesconnection of the individual fuel cells. Positive electrical connection50 and negative electrical connection 48 allow an external load to beconnected to the fuel cell layer, which produces a voltage that is amultiple of the single cell voltages produced within the fuel celllayer.

FIG. 7 shows a similar view as FIG. 6 of the fuel cell layer 64 but inthis Figure, each of the fuel cells 8 have a channel 14 with a lessstraight structure. Again, as with FIG. 6, FIG. 7 uses essentially thesame structure as shown in FIGS. 4 and 5, but repeated multiple timescreating a multi-cell structure. The less straight structure of thechannels allows for increased electrochemically active areas for theanodes and cathodes formed on the channel walls. The less straightchannels can be smoothly undulating or can be irregular in shaperesembling a fractral structured path which is known to have extremelyhigh area. Any arbitrary channel structure can be used with thisinvention allowing for the optimization of the area of the electrodes ineach fuel cell. A preferred embodiment includes a plurality of thinchannels that run parallel to each other and follow an irregular paththat folds back on itself in a manner suggestive of a fractal pattern.Another preferred embodiment of the invention includes at least onechannel that is in at least three planes.

FIG. 8 shows a perspective view of a cylindrical version 250 of amultiple fuel cell layer. In this version a multitude of non-planar fuelcells 208 are combined to create a fuel cell layer 64 that encloses avolume 210. The enclosed volume 210 is used as the fuel plenum whileoxidant is supplied by the environment outside the cell. It is alsoenvisioned that the fuel be supplied by the environment outside thecylinder and that the enclosed volume 210 be used as an oxidant plenum.The cylindrical fuel cell 250 can either be constructed using a singleporous substrate which is in the shape of a cylinder using the methoddiscussed for combining cells in FIG. 5 or with multiple poroussubstrates that are brought together into a cylinder using the methoddiscussed for combining cells in FIG. 4.

FIG. 8 a is a cross-section of a non-planar version of the fuel cell208. The fuel cell has a fuel plenum 10 with fuel inlet 18 and fueloutlet 20 and an oxidant plenum 16 with oxidant inlet 52 and oxidantoutlet 54. A non-planar porous substrate 212 is in communication withboth the fuel plenum 10 and the oxidant plenum 16. A channel 14 isformed within the non-planar porous substrate 212. The channel 14 has ananode 40 and a cathode 38 constructed as described for FIG. 1 and isfilled with electrolyte 32. The fuel cell has a support member 26 afirst coating 34 and a second coating 36. The negative electricalconnector 48 is shown adjacent sealant barrier 46. The positiveelectrical connector 50 is shown adjacent the optional sealant barrier44. Although in this figure an arc is used to show the non-planar natureof the fuel cell, any arbitrary configuration could be used. As with thefuel cells of FIG. 1 the non-planar fuel cell can be combined to form anon-planar fuel cell layer with multiple cells and can be associatedwith fuel and optional oxidant plenums of various configurations.

FIG. 9 shows a cross sectional view of a cylindrical version of a fuelcell. In this case the non-planar substrate 212 is shaped in the form ofa cylinder to enclose a volume 210. The fuel cell in this figure isshown with fuel 11 in the enclosed volume 210 providing fuel to the fuelcell. In this configuration the ambient environment outside the cellsupplies oxidant. It is also envisioned that oxidant be contained withinthe enclosed volume 210 and that the ambient environment supply thefuel.

FIG. 10 is another embodiment of a cylindrical fuel cell 251 having thechannels 14 of the non-planar fuel cells 208 configured radially andorthogonal to the axis of the cylinder. It is understood that the fuelcells 208 within this figure can either be constructed or assembled, asdescribed for FIG. 4 or that they be formed within a single cylindricalsubstrate as described for FIG. 5.

FIG. 11 is another embodiment of a cylindrical fuel cell 252 having thechannel 14 of the non-planar fuel cell disposed in a wound or spiralfashion around the perimeter of the cylinder. Although, in this figure,only a single spiral channel 14 is shown, multiple fuel cells withmultiple channels could be formed using the porous substrate.

Although only cylindrical cells have been shown enclosing a volume it iscontemplated herein that shapes such as extruded rectangles, squares,ovals, triangles and other shapes as well as non-extruded shapes such ascones, pyramids, football shaped objects and other shapes that enclose avolume are included as part of the invention.

FIG. 12 is a cutaway perspective view of a bi-level fuel cell layerstructure 254 with two fuel cell layers, a first fuel cell layer 64 anda second fuel cell layer 112 each comprising an anode side and a cathodeside wherein said first fuel cell layer 64 is stacked on top of saidsecond fuel cell layer 112 such that the anode side 264 of the firstfuel cell layer and the anode side 268 of the second fuel cell layeradjoin.

In this Figure, a seal 130 is disposed between the first and second fuelcell layer to form a fuel plenum 124. The two positive electricalconnections are connected to positive connector 120 and the two negativeelectrical connections are connected to negative connector 122 so thatthe individual fuel cell layers are now connected in an electricallyparallel configuration. The resulting assembly is a bi-level fuel celllayer structure 254 having a top 70 and a bottom 72, the top and bottombeing the cathode sides of the respective fuel cell layers. Theresulting structure is an enclosed plenum air breathing fuel cell thatachieves a series electrical connection of the individual fuel cells ineach fuel cell layer and a parallel electrical connection of the twofuel cell layers. Only fuel is required to be fed to the interior of thestructure and electrical current flows within the two fuel cell layersindependently of one another. There is no electrical connection betweenthe two fuel cell layers except at the parallel connection of thepositive and negative electrical connections at either end of the fuelcell layers in the structure.

It is also envisioned that the fuel cell layers be placed cathode tocathode thereby creating a common plenum that can be filled withoxidant. In this configuration the fuel cell sandwich uses the ambientenvironment as a fuel supply.

Although various materials could be used for the porous substrate of theinvention, one usable material could be a conductive material. Materialssuch as a metal foam, graphite, graphite composite, at least one siliconwafer, sintered polytetrafluoroethylene, crystalline polymers,composites of crystalline polymers, reinforced phenolic resin, carboncloth, carbon foam, carbon aerogel, ceramic, ceramic composites,composites of carbon and polymers, ceramic and glass composites,recycled organic materials, and combinations thereof are contemplated asusable in this invention.

The channel is contemplated to have up to 50 optional support membersseparating the walls of the channel. The support members can be locatedat the extreme ends of the channel, such as forming a top or bottom, orcan be located in the middle portion of the channel, or be oriented atan angle to the center of the channel. It is contemplated that thesupport member can be an insulating material. If an insulating materialis used, it is contemplated that silicon, graphite, graphite composite,polytetrafluoroethylene, polymethylmethacrylate, crystalline polymers,crystalline copolymers, cross-linked polymers thereof, wood, andcombinations thereof can be usable in the invention.

Dimensionally, the channel can have a dimension ranging from 1 nanometerto 10 cm in height, 1 nanometer to 1 mm in width and from 1 nanometer to100 meters in length.

A single fuel cell of the invention, optionally within a fuel celllayer, is contemplated of being capable of producing betweenapproximately 0.25 volts and approximately 4 volts. Between 1 and 5000fuel cells are contemplated as usable in one fuel cell layer in thisdesign, however in a preferred embodiment, the fuel cell layer hasbetween 75 and 150 joined fuel cells. This fuel cell layer iscontemplated to be capable of producing a voltage between 0.25 volts and2500 volts. A fuel cell with more channels will be capable of producinghigher voltages.

The invention can be constructed such that the fuel comprises a memberof the group: pure hydrogen, gas containing hydrogen, formic acid, anaqueous solution comprising a member of the group: ammonia, methanol,ethanol and sodium borohydride, and combinations thereof. The inventioncan be constructed such that the oxidant comprises a member of thegroup: pure oxygen, gas containing oxygen, air, oxygen enriched air, andcombinations thereof.

Electrolyte usable in this invention can be a gel, a liquid or a solidmaterial. Various materials are contemplated as usable and include: aperfluoronated polymer containing sulphonic groups, an aqueous acidicsolution having a pH of at most 4, an aqueous alkaline solution having apH greater than 7, and combinations thereof. Additionally, it iscontemplated that the electrolyte layer can be between 1 nanometer and1.0 mm in thickness, or alternatively simply filling each undulatingchannel from first wall to second wall without a gap.

The fuel cell is manufactured using a first and second coating on theporous substrate. These coatings can be the same material or differentmaterials. At least one of said coatings can comprise a member of thegroup: polymer coating, epoxies, polytetrafluoroethylene,polymethylmethacrylate, polyethylene, polypropylene, polybutylene, andcopolymers thereof, cross-linked polymers thereof, conductive metal, andcombinations thereof. Alternatively, the first or second coating cancomprise a thin metallic layer such as a coating of gold, platinum,aluminum or tin as well as alloys of these or other metals or metalliccombinations.

The first and second catalyst layers that are contemplated as usable inthe invention can be a noble metal, alloys comprising noble metals,platinum, alloys of platinum, ruthenium, alloys of ruthenium, andcombinations of these materials. It is contemplated that ternary alloyshaving at least one noble metal are usable for good voltage creation.Platinum-ruthenium alloys are also contemplated as usable in thisinvention. The catalyst layers should each have a catalyst loadingquantity wherein the amount of catalyst may be different for each layer.

The material for said optional sealant barriers contemplated herein canbe selected from the group comprising: silicon, epoxy, polypropylene,polyethylene, polybutylene, and copolymers thereof, composites thereof,and combinations thereof.

One method for making the fuel cell contemplates the following steps:

-   -   a. forming a porous substrate having a top and bottom having a        first side and a second side;    -   b. coating at least a portion of said top with a first coating;    -   c. coating at least a portion of said bottom with a second        coating;    -   d. forming a channel using the porous substrate, wherein said        channel comprises a first channel wall and a second channel        wall;    -   e. forming an anode by depositing a first catalyst layer on said        first channel wall;    -   f. forming a cathode by depositing a second catalyst layer in        said second channel wall;    -   g. disposing electrolyte in at least a portion of the channel        contacting the anode and the cathode;    -   h. attaching a positive electrical connection on one end to the        first side of said porous substrate, and attaching a negative        electrical connection on one end to said second side of said        porous substrate;    -   i. attaching a fuel plenum to the porous substrate forming a        fuel cell;    -   j. attaching an oxidant plenum to the porous substrate;    -   k. disposing a sealant barrier around at least a portion of said        fuel cell; and    -   l. loading said fuel plenum with fuel and said oxidant plenum        with oxidant.

The sequence of operations described may be varied and steps combined asrequired to suit the particular material requirements and fabricationprocesses used. As well, the method can comprise forming between one and250 or more channels in said porous substrate.

Another method for forming a fuel cell envisioned in the inventioncontemplates the following steps:

-   -   a. repeating steps a through h of the method above as many times        as needed prior to joining the porous substrate to the fuel        plenum forming at least one additional fuel cell;    -   b. securing the porous substrate at the sealant barriers to at        least on additional fuel cell at its sealant barrier forming a        fuel cell layer and extending said fuel cell layer securing        additional formed fuel cells to the fuel cell layer at        respective sealant barriers;    -   c. attaching the positive electrical connections and the        negative electrical connections of the fuel cell layer together;    -   d. attaching the joined fuel cells to said fuel plenum; and    -   e. attaching the joined fuel cells to said oxidant plenum.

The positive electrical connections and the negative electricalconnections of said fuel cells within the fuel cell layer can beconnected in series, in parallel or in a combination of series andparallel.

Yet another method for making a fuel cell layer is contemplated whichhas the steps of:

-   -   a. forming a porous substrate comprising a top and bottom, a        first side and a second side;    -   b. coating at least a portion of said top with a first coating;    -   c. coating at least a portion of said bottom with a second        coating;    -   d. forming a plurality of distinct channels using the porous        substrate, wherein each distinct channel comprises a first        channel wall and a second channel wall;    -   e. forming a plurality of anodes by depositing a plurality of        first catalyst layers on said first channel walls;    -   f. forming a plurality of cathodes by depositing a plurality of        second catalyst layers in said second channel walls;    -   g. disposing electrolyte in at least a portion of each distinct        channel;    -   h. disposing a first sealant barrier on at least a portion of        said first side;    -   i. disposing a second sealant barrier on at least a portion of        said second side;    -   j. forming a plurality of third sealant barriers between each of        said distinct channels creating a plurality of independent fuel        cells adjacent each other in the porous substrate;    -   k. attaching a positive electrical connection to the first side        of said porous substrate;    -   l. attaching a negative electrical connection to said second        side of said porous substrate;    -   m. attaching a fuel cell positive electrical connection to each        independent fuel cells    -   n. attaching a fuel cell negative electrical connection to each        independent fuel cell forming a fuel cell layer; and    -   o. disposing a sealant barrier around at least a portion of said        fuel cell layer.

In any of the methods described above a number of different methods offorming said porous substrate are contemplated herein. The poroussubstrate can be formed by a method that is a member of the groupcomprising: casting and then baking, slicing layers from a pre-formedbrick, molding, extruding, and combinations thereof. The formed poroussubstrate may be non-planar or enclose a volume.

If at least one of the coatings is deposited with thin film depositiontechniques, the technique may include a member of the group comprising:sputtering, electroless plating, electroplating, soldering, physicalvapor deposition, chemical vapor deposition. If at least one of thecoatings is an epoxy coating the coating can be disposed on saidsubstrate by a method selected from the group: screen printing, ink jetprinting, spreading with a spatula, spray gun deposition, vacuum baggingand combinations thereof. A mask can be used when applying said coatingsto said porous substrate. If required, a portion of the coating can beremoved prior to adding the electrolyte.

The channel can be formed in the porous substrate by a method selectedfrom the group comprising: embossing, ablating, etching, extruding,laminating, embedding, melting, molding, cutting, and combinationsthereof. If etching is used, the etching can be by a method selectedfrom the group comprising: laser etching, deep reactive ion etching, andalkaline etching. Alternatively, it is anticipated the channels can beformed by micro-milling using laser cutting, high pressure waterjets,micro-dimensioned rotary tools or mechanical dicing saws.

Within the invention it is envisioned to deposit the electrolyte in saidchannel using a method that is a member of the group comprising:pressure injection, vacuum forming, hot embossing, and combinationsthereof.

The variations for making the apparatus can be implemented into any ofthe methods described above. For example, the method can contemplateusing a conductive material for the sealant barrier and/or an insulationmaterial for the support member.

The fuel cell of the invention can be used by first, connecting a fuelsource to a fuel plenum inlet; second, connecting a fuel plenum outletto a re-circulating controller; third, connecting an oxidant plenuminlet to an oxidant source; fourth, connecting an oxidant plenum outletto a flow control system, fifth, connecting a positive electricalconnection and a negative electrical connection to an external load;sixth, flowing fuel and oxidant to the inlets; and finally, driving loadwith electricity produced by the fuel cell.

If a dead-ended version of the fuel cell is used the operation is muchsimpler. First, the fuel inlet is connected to a fuel supply, second,the oxidant inlet is connected to an oxidant supply, third, the positiveelectrical connection and the negative electrical connection areconnected to an external load; and finally, the load is driven withelectricity produced by the fuel cell.

The method of the invention can further comprise the step of sealing theplenum outlets and inlets after the fuel and oxidant is loaded intotheir respective plenums creating a dead ended fuel cell. The fuel cellcan then be connected to an external load using the positive andnegative electrical connections and used to drive the external load.

It is envisioned within this invention to use any combination of fueland oxidant inlets and outlets to operate the fuel cell.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the scope of theinvention.

1. A fuel cell layer comprising: a. a fuel plenum comprising fuel; b. anoxidant plenum comprising oxidant; c. a plurality of fuel cells, whereineach fuel cell comprises: i. a porous substrate communicating with saidfuel plenum and said oxidant plenum, wherein said porous substratefurther comprises a top, a bottom, a first side and a second side; ii. achannel formed using said porous substrate, wherein said channelcomprises a first channel wall and a second channel wall; iii. an anodeformed from a first catalyst layer disposed on the porous substrate ofsaid first channel wall; iv. a cathode formed from a second catalystlayer disposed on the porous substrate of said second channel wall; v.electrolyte disposed in at least a portion of said channel contactingthe anode and the cathode preventing transfer of fuel to the cathode andpreventing transfer of oxidant to the anode; vi. a first coatingdisposed on at least a portion of said porous substrate to prevent fuelfrom entering a portion of at least a portion of said porous substrate;vii. a second coating disposed on at least a portion of said poroussubstrate to prevent oxidant from entering at least a portion of saidporous substrate; viii. a first sealant barrier disposed on the firstside and the second sealant barrier disposed on the second side; ix. apositive electrical connection disposed on said first side; and x. anegative electrical connection disposed on said second side; d. andwherein said plurality of fuel cells comprise at least a first fuel cellconnected to at least a second fuel cell at said sealant barriersforming a fuel cell assembly which is connected to said fuel plenum andto said oxidant plenum, and wherein said fuel cell assembly generates acurrent to drive an external load.
 2. The fuel cell layer of claim 1,wherein said anodes formed from said first catalyst layers are disposedin the porous substrate of said first channel walls; and said cathodesformed from said second catalyst layers are disposed in the poroussubstrate of said second channel walls.
 3. The fuel cell layer of claim2, wherein said first and second catalyst layers are disposed in theporous substrates at least at a minimum depth to cause catalyticactivity.
 4. The fuel cell layer of claim 1, wherein said channels areformed within said porous substrates.
 5. The fuel cell layer of claim 4,wherein said channels are formed using a technique selected from thegroup consisting of cutting, ablating, molding, etching, extruding,embossing, laminating, embedding, melting, and combinations thereof. 6.The fuel cell layer of claim 1, wherein at least one of said channels isundulating.
 7. The fuel cell layer of claim 1, wherein at least one ofsaid channels is in at least three planes.
 8. The fuel cell layer ofclaim 1, wherein said oxidant comprises a member of the group consistingof pure oxygen, gas containing oxygen, air, oxygen enriched air, andcombinations thereof.
 9. The fuel cell layer of claim 1, wherein saidfuel comprises a member of the group consisting of pure hydrogen, gascontaining hydrogen, formic acid, and an aqueous solution, wherein theaqueous solution is a member of the group consisting of ammonia,methanol, ethanol, sodium borohydride, and combinations thereof.
 10. Thefuel cell layer of claim 1, wherein at least one of said poroussubstrates comprises a planar shape.
 11. The fuel cell layer of claim 1,wherein said plurality of fuel cells comprise a shape that encloses avolume.
 12. The fuel cell layer of claim 1, wherein said shape of saidplurality of fuel cells comprises a cylinder.
 13. The fuel cell layer ofclaim 1, wherein at least one of said porous substrates is a conductivematerial.
 14. The fuel cell layer of claim 1 wherein at least one ofsaid porous substrates comprises a member of the group consisting of ametal foam, graphite, graphite composite, at least one silicon wafer,sintered polytetrafluoroethylene, crystalline polymers, composites ofcrystalline polymer, reinforced phenolic resin, carbon cloth, carbonfoam, carbon aerogel, ceramic, ceramic composites, composites of carbonand polymers, ceramic and glass composites, recycled organic material,and combinations thereof.
 15. The fuel cell layer of claim 1, wherein atleast one of said fuel cells further comprises: a support memberdisposed between the first channel wall and the second channel wall, andsaid support member comprises a member of the group consisting ofsilicon, graphite, graphite composite, polytetrafluoroethylene,polymethylmethacrylate, crystalline polymers, crystalline copolymers,cross-linked polymers thereof, wood, and combinations thereof.
 16. Thefuel cell layer of claim 1, further comprising a fuel plenum outletconnected to said fuel plenum.
 17. The fuel cell layer of claim 1,further comprising a fuel plenum inlet connected to the fuel plenum. 18.The fuel cell layer of claim 1, further comprising an oxidant plenuminlet in communication with the oxidant plenum.
 19. The fuel cell layerof claim 1, further comprising an oxidant plenum outlet in communicationwith the oxidant plenum.
 20. The fuel cell layer of claim 1, whereinsaid fuel plenum comprises a permeable material.
 21. The fuel cell layerof claim 1, wherein said fuel plenum comprises a solid material with aflow field.
 22. The fuel cell layer of claim 1, wherein said fuel plenumis an open to an ambient environment.
 23. The fuel cell layer of claim1, wherein at least one of said fuel cells comprises an electrolyteselected from the group comprising: a perfluoronated polymer containingsulphonic groups, an aqueous acidic solution having a ph of greater than7, an aqueous alkaline solution having a ph of at most 4, andcombinations thereof.
 24. The fuel cell layer of claim 1, wherein atleast one fuel cell comprises a first coating and a second coating ofthe same material.
 25. The fuel cell layer of claim 1, wherein at leastone fuel cell comprises a first coating and a second coating ofdifferent materials.
 26. The fuel cell layer of claim 1, wherein atleast one of said coatings can comprise a member of the group consistingof polymer coating, epoxies, polytetrafluoroethylene,polymethylmethacrylate, polyethylene, polypropylene, polybutylene, andcopolymers thereof, cross-linked polymers thereof, conductive metal andcombinations thereof.
 27. The fuel cell layer of claim 1, wherein atleast one of said catalyst layers is a member of the group consisting ofnoble metals, alloys comprising noble metals, platinum, alloys ofplatinum, ruthenium, alloys of ruthenium, and combinations thereof. 28.The fuel cell layer of claim 27, wherein at least one of said catalystlayers is a ternary alloys comprising at least one noble metal.
 29. Thefuel cell layer of claim 27, wherein at least one of said catalystlayers is platinum.
 30. The fuel cell layer of claim 27, wherein atleast one of said catalyst layers is a platinum-ruthenium alloy.
 31. Thefuel cell layer of claim 27, wherein at least one of said catalystlayers has a different catalyst loading quantity from other catalystlayers.
 32. The fuel cell layer of claim 1 wherein at least one of saidchannels has a dimension a height ranging from 1 micron to 10 cm, awidth ranging from 1 nanometer to 1 mm, and a length ranging from 1nanometer to 100 meters.
 33. The fuel cell layer of claim 1, whereinsaid fuel cell layer produces a voltage between approximately 0.25 voltsand approximately 2500 volts.
 34. The fuel cell layer of claim 1,wherein said fuel plenum has a rectangular cross-section.
 35. The fuelcell layer of claim 1, wherein said oxygen plenum comprises a permeablematerial.
 36. The fuel cell layer of claim 1, wherein said oxygen plenumcomprises a solid material with a flow field.
 37. The fuel cell layer ofclaim 1, wherein said oxygen plenum is open to an ambient environment.38. The fuel cell layer of claim 1, wherein said fuel cell layercomprises between 1 joined fuel cells and 5000 joined fuel cells. 39.The fuel cell layer of claim 38, wherein said fuel cell layer comprisesbetween 75 joined fuel cells and 150 joined fuel cells. Additionally theporous substrate 12 has first side 104 and a second side 106.